Project Summary/Abstract Retinal and choroidal vascular diseases, which include neovascular age-related macular degeneration (NVAMD), diabetic retinopathy (DR), and retinal vein occlusions (RVO), are by far the most prevalent causes of moderate and severe vision loss in the US. During past grant periods, our laboratory helped to identify and validate vascular endothelial growth factor (VEGF) as a critical stimulator. VEGF antagonists have now become standard care for NVAMD and macular edema due to DR or RVO. This has provided tremendous benefit to large numbers of patients, but concern has been raised that VEGF antagonists cause retinal damage. During the past grant period, we demonstrated that VEGF antagonists do not damage normal retina, but it is still possible that they may make the retina more susceptible to damage from stress. In the first aim, this hypothesis will be thoroughly investigated. While VEGF antagonists have provided tremendous benefit for patients with the above disease processes, there are still a large number of patients who have incomplete or little response and need something more. Other stimulators have been identified and one strategy is to add antagonists to each of them resulting in multi- drug combination therapy. However, VEGF and the other stimulators are all upregulated by hypoxia-inducible factor-1 (HIF-1) and in the second aim we will investigate the strategy of using HIF-1 antagonists to achieve single drug combination therapy. Tie2 is an endothelial cell receptor that when stimulated makes blood vessels unresponsive to VEGF and the other stimulators and hence blocks neovascularization and excessive leakage. In the third aim, we will explore a second novel approach to obtain single drug combination therapy by keeping Tie2 in an activated state with an antagonist to a specific Tie2 phosphatase, human protein tyrosine phosphatase-b (HPTP-b). The potential impact of this proposal is high because it will provide important information regarding the effects of blocking VEGF in the retina, which is a rapidly growing treatment for several retinal diseases. In addition, the proposal uses novel strategies to simultaneously suppress additional stimulators in addition to VEGF and determine if there are any benefits and/or adverse consequences for doing so. Based upon past successes, it is reasonable to predict that findings from this proposal will lead to new clinical trials.